Short-range automobile wireless communication device

ABSTRACT

In a short-range on-vehicle radio communication system having in-car radio communication function, a two-way transmission antenna for radio communication is arranged at a panel portion outside a sheet metal chassis of a car navigation unit. As a result, the communication area becomes large, signals including those from a cellular phone of low radio communication output power are easily received, and it is possible to save manufacturing cost.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP00/08561 which has an Internationalfiling date of Dec. 4, 2000, which designated the United States ofAmerica.

FIELD OF THE INVENTION

The present invention relates to an arrangement of a two-waytransmission antenna for radio communication in a short-range on-vehicleradio communication system having in-car radio communication function.

BACKGROUND ART

FIG. 15 is a block diagram of a conventional hands-free system. Acellular phone base station 1 and a cellular phone 2 are connected via apublic radio communication line. Signals are transmitted and receivedbetween the cellular phone 2 and a hands-free unit 3 via a connector 2Cprepared in the cellular phone 2. A microphone 4 and a speaker 5 areconnected to the hands-free unit 3. Telephone signals gathered by themicrophone 4 arranged in a vehicle are transmitted to the cellular phonebase station 1 via the hands-free unit 3 and the cellular phone 2. Then,the telephone signals are transmitted from the cellular phone basestation 1 to a person on the other end of a so-called public telephoneline. On the other hand, telephone signals from the person on the otherend of the line are transmitted to the hands-free unit 3 through thereverse path. The speaker 5 reproduces the telephone signals from theperson on the other end of the line inputted to the hands-free unit 3.The cellular phone 2, the hands-free unit 3, the microphone 4 and thespeaker 5 are arranged in the vehicle 6.

The hands-free system shown in FIG. 15 has a disadvantage in the aspectthat it is necessary to connect the connector 2C of the cellular phone 2every time a cellular phone user gets on the vehicle. Moreover, it isalso necessary to disconnect the connector 2C when the user gets out ofthe vehicle. Furthermore, when the connector 2C is not connected, theconnector 2C with cable should be put away to avoid the car room fromlooking not neat.

FIG. 16 is a block diagram of another conventional hands-free system,which overcomes the mentioned disadvantage of the hands-free system ofFIG. 15. The hands-free system shown in FIG. 16 is disclosed, forexample, in the Japanese Patent Publication (unexamined) No. 276261/1998titled “Radio Communication System”. A difference from the hands-freesystem of FIG. 15 consists in that the, instead of the cable system, thecellular phone 2 a and the hands-free unit 3 a are connected by a radiosystem (or an infrared system). Flow of the telephone signals is thesame as in the case of FIG. 15, and further description thereof isomitted herein. In another known system disclosed in the Japanese PatentPublication (unexamined) No. 331064/1999 titled “Hands-free TelephoneSystem”, a radio (FM) circuit portion built in the cellular phone 2 abody is formed into a radio module 7 and is arranged at a connectorportion of the cellular phone 2 a.

The disadvantages of connecting and disconnecting the connector of thecellular phone 2 a and looking not neat are overcome by using the radiosystem (or the infrared system) in connecting the cellular phone 2 a andthe hands-free unit 3 a. In the case of the infrared system, it isnecessary that infrared transmitting and receiving sections of thecellular phone 2 a and the hands-free unit 3 a are arranged opposite toeach other. On the contrary, in the case of the radio system, it is notnecessary that the transmitting and receiving sections of the cellularphone 2 a and the hands-free unit 3 a are arranged opposite to eachother.

As a short-range radio communication system of such type, Bluetooth SIGhas proposed a “Bluetooth” system. (BLUETOOTH is a registered trademarkof Telefonaktiebolaget L M Ericsson, Sweden.)

The mentioned system has the following characteristics:

-   (1) Cordless communication between one apparatus and another is    achieved.-   (2) Radio circuit of this system is applicable to a variety of    apparatuses such as personal computers, printers, cellular phones,    personal digital assistants, etc.-   (3) The global standard is adopted.-   (4) Both voice and data communication can be transmitted and    received.-   (5) A frequency band of 2.4 GHz called an ISM band is adopted.-   (6) It is not necessary to arrange the communication apparatuses    opposite to each other unlike those in the infrared communication.-   (7) Communication between apparatuses is available in the form of    not only 1 to 1 like the infrared communication but also 1 to 7    (maximum).-   (8) It is possible to choose any output power convenient for each    apparatus because there are following three types of outputs:-   Class 1: 100 mW (+20 dBm) max;-   Class 2: 2.5 mW (+4 dBm) max; and-   Class 3: 1 mW (0 dBm) max.

In choosing one output power among the three types described in theforegoing characteristic (8) of the system, Class 3 of the smallestpower consumption (i.e., the battery life is long) for a portable devicesuch as cellular phone. It is preferable to adopt Class 1 from theviewpoint of giving an importance to a communication area such as homemodem station where communication with each room is available on thepower-saving basis.

Supposing that a radio communication is conducted using a cellular phonehaving a small radio communication output power function like in theforegoing system with a cellular phone brought into a vehicle, it ispossible to utilize this radio communication enjoying the followingadvantages: p0 (1) Hands-free telephone

-   {circle around (1)} Cordless and hands-free telephone is available    even when the cellular phone is put in a bag, on a rear seat, or the    like.-   {circle around (2)} This contributes to safe driving.-   (2) Information and communication display-   {circle around (1)} Information provided by an IT-adapted cellular    phone of a mobile communication company is displayed on a map    display of a car navigation unit. The information is enlarged on the    display and easy to see.-   {circle around (2)} Plural persons in the vehicle can see the    display at the same time.-   {circle around (3)} This contributes to safe driving.

Now, environment of the radio communication is described below.

-   (1) A power-saving type is adopted as the radio output power of the    cellular phone in most cases.-   {circle around (1)} In the case of power-saving output power, it is    considered that communication is available within a distance of    several meters.-   (2) In the cases of the foregoing hands-free telephone (1) and    information and communication display (2), a radio communication    circuit is built in a car navigation unit in most cases.-   {circle around (1)} As the car navigation unit is composed of a    sheet metal chassis, a radio communication antenna is arranged    inside the sheet metal chassis of the car navigation unit, and    therefore sensitivity is low.-   {circle around (2)} The car navigation unit is arranged at any of    various places such as center console, under side of seat, and    trunk.-   {circle around (3)} In the case of arranging the car navigation unit    in the trunk, to be free from outside influence such as “pressure”,    “waterdrop”, and the like from loaded cargo, the unit incorporating    the communication antenna of the car navigation may be further    covered with a sheet metal when required.

Accordingly, an object of the invention is to provide a short-rangeon-vehicle radio communication system having in-car radio communicationfunction, capable of widening the communication area so that any signalfrom a cellular phone of low radio communication output power asdescribed above may be easily received.

DISCLOSURE OF INVENTION

The invention provides a short-range on-vehicle radio communicationsystem having an in-car radio communication function, in which a two-waytransmission antenna for radio communication is arranged outside a sheetmetal chassis of a main body. As a result of employing such anarrangement, communication area becomes larger and any signal from acellular phone of low radio communication output power might be easilyreceived.

The invention is applied to a car navigation unit, and the two-waytransmission antenna for radio communication is arranged at a panelportion outside the sheet metal chassis of the car navigation unit. As aresult of employing such an arrangement, communication area becomesbroader, any signal from a cellular phone of low radio communicationoutput power might be easily received, and it is further possible tosave the manufacturing cost.

The invention provides the short-range on-vehicle radio communicationsystem having in-car radio communication function, in which the two-waytransmission antenna for radio communication is arranged outside themain body. As a result of employing such an arrangement, a stable andlarge communication area is secured irrespective of the place oflocating the short-range on-vehicle radio communication system mainbody, and any signal from a cellular phone of low radio communicationoutput power might be easily received.

The invention provides the system of the short-range radio communicationof which radio communication output power is small, which is applied tothe car navigation unit. As a result of employing such an arrangement,the problem of communication antenna being low in sensitivity is solved,and any signal from a cellular phone of low radio communication outputpower of several meters in communication available distance is might beeasily received.

The invention provides the short-range on-vehicle radio communicationsystem having in-car radio communication function, in which the two-waytransmission antenna for radio communication is arranged at a ceiling ina car room. As a result of employing such an arrangement, influence dueto the place where the person to communicate to (i.e., the cellularphone) is located in the car room, is less. Furthermore, difference indistance between each place where the main body of the short-rangeon-vehicle radio communication system is located in the vehicle and thetwo-way transmission antenna for radio communication is reduced, andtherefore fluctuation in loss caused by cable length is restrained.

The invention provides the short-range on-vehicle radio communicationsystem having in-car radio communication function, in which the two-waytransmission antenna for radio communication is arranged in an interiorlight module on the ceiling in the car room, on a surface of the module,or around the module. As a result of employing such an arrangement, thetwo-way transmission antenna for radio communication is out of sight,and wiring can be performed together with wiring for the interior light.The antenna can be arranged on the ceiling together with the interiorlight module. Further, the influence due to the place where the personto communicate to (i.e., the cellular phone) is located in the car roomis reduced. Difference in distance between each place where the mainbody of the short-range on-vehicle radio communication system isarranged in the vehicle and the two-way transmission antenna for radiocommunication is less, and therefore fluctuation in loss caused by thecable length is restrained.

The invention provides the short-range on-vehicle radio communicationsystem having in-car radio communication function, in which the two-waytransmission antenna for radio communication is arranged on the frontseat side. As a result of employing such an arrangement, the two-waytransmission antenna for radio communication is located in the vicinityof the cellular phone brought into the vehicle by a driver who uses thehands-free telephone in most cases, which increases reliability intransmitting and receiving through the radio communication.

The invention provides the short-range on-vehicle radio communicationsystem having in-car radio communication function, in which the two-waytransmission antenna for radio communication is arranged on an outercircumference of the main body. As a result of employing such anarrangement, the antenna cable is shortened and loss due to cable lengthis less. Further the antenna mounting work becomes easy.

The invention provides the short-range on-vehicle radio communicationsystem having in-car radio communication function, in which pluraltwo-way transmission antennas for radio communication are arrangedoutside the sheet metal chassis of the main body in the vehicle. As aresult of employing such an arrangement, the communication-availablearea becomes highly reliable, which enables development for large-sizedvehicles such as buses.

The invention provides the short-range on-vehicle radio communicationsystem having in-car radio communication function, in which among theplural two-way transmission antennas for radio communication, one isarranged at a front portion inside the vehicle and another one isarranged at a rear portion inside the vehicle.

The invention provides the short-range on-vehicle radio communicationsystem having in-car radio communication function, in which among theplural two-way transmission antennas for radio communication, one isarranged at a panel portion outside the sheet metal chassis and anotherone is arranged outside the main body.

Furthermore, the invention provides the short-range on-vehicle radiocommunication system having in-car radio communication function, inwhich an antenna output of the highest reception level is selected amongthe plural two-way transmission antennas for radio communication. As aresult of employing such an arrangement, when the person to communicateto uses a communication apparatus of small communication output power,the communication is secured even when the person to communicate tomoves. This enables development for large-sized vehicles such as buses.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing an arrangement according toEmbodiment 1 of the invention.

FIG. 2 is a schematic diagram showing an arrangement according toEmbodiment 2 of the invention.

FIG. 3 is a schematic view showing an arrangement according toEmbodiment 3 of the invention.

FIG. 4 is a schematic view showing an arrangement according toEmbodiment 4 of the invention.

FIG. 5 is a schematic view showing an arrangement according toEmbodiment 5 of the invention.

FIG. 6 and FIG. 7 are a schematic view and a perspective viewrespectively showing an arrangement according to Embodiment 6 of theinvention.

FIG. 8 is a perspective view showing an arrangement according toEmbodiment 7 of the invention.

FIG. 9 is a perspective view showing an arrangement according toEmbodiment 8 of the invention.

FIG. 10 is a schematic view showing an arrangement according toEmbodiment 9 of the invention.

FIG. 11 is a schematic view showing an arrangement according toEmbodiment 10 of the invention.

FIG. 12 is schematic view showing an arrangement according to Embodiment11 of the invention.

FIG. 13 is a schematic view showing an arrangement according toEmbodiment 12 of the invention.

FIG. 14 is a block diagram showing Embodiment 13 of the invention, andis a block diagram of an antenna output selection circuit showing anessential part of Embodiment 12.

FIG. 15 is a block diagram of a conventional hands-free system.

FIG. 16 is a block diagram of another conventional hands-free system.

BEST MODE FOR CARRYING OUT THE INVENTION

In the case of performing a radio communication between a cellular phoneand an on-vehicle radio communication system (a car navigation unit), apower-saving type output power is adopted as the radio output power ofthe cellular phone in most cases.

On the other hand, the on-vehicle radio communication system (the carnavigation unit) is covered with a sheet metal chassis except for apanel face.

Embodiment 1.

Taking account of the foregoing conditions, Embodiment 1 of theinvention is hereinafter described with reference to FIG. 1. FIG. 1 is aschematic diagram showing an arrangement according to Embodiment 1 ofthe invention. It is supposed herein that a short-range radiocommunication is performed between a cellular phone 2 b and a carnavigation unit 8 (a short-range on-vehicle radio communication system)each having short-range radio communication function. In this case, if atwo-way transmission antenna 9 a for short-range radio communication inthe can navigation unit 8 is arranged inside a sheet metal chassisportion 8 b, radiation pattern characteristic of the two-waytransmission antenna 9 a for radio communication is restricted, and anarea where communication is available becomes narrow. In order to relaxthe restriction on the radiation pattern characteristic of the two-waytransmission antenna 9 a for radio communication, the two-waytransmission antenna 9 a for radio communication is arranged outside thesheet metal chassis portion 8 b of the can navigation unit 8, i.e., at apanel portion 8 c.

As a result, the communication area becomes large, and this improvesreception of signals including those from the cellular phone 2 b of lowshort-range radio communication output power. It is possible to save themanufacturing cost by arranging the two-way transmission antenna 9 a forradio communication at the panel portion 8 c outside the sheet metalchassis portion 8 b of the car navigation unit 8.

The car navigation unit 8 has hands-free function, and to which themicrophone 4 and the speaker 5 is connected. The cellular phone 2 b, thecar navigation unit 8, the microphone 4, and the speaker 5 are alllocated in the vehicle 6. Telephone signals gathered by the microphone 4arranged in the vehicle 6 are transmitted to the cellular phone basestation 1 via the car navigation unit 8 and the cellular phone 2 b. Onthe other hand, telephone signals from the person on the other end ofthe line are transmitted to the car navigation unit 8 through thereverse path. The speaker 5 reproduces telephone signals of the personon the other end of the line inputted to the car navigation unit 8. Itis a matter of course that the system shown in FIG. 1 is also applicableto a case of displaying data other than the telephone signals from thecellular phone 2 b on the map display (not shown) for the car navigationunit 8, and to a case of transmitting data other than the telephonesignals from the car navigation unit 8 to the cellular phone 2 b.

Embodiment 2.

FIG. 2 is a schematic diagram showing an arrangement according toEmbodiment 2 of the invention. In this Embodiment 2, the two-waytransmission antenna 9 a for short-range radio communication of the cannavigation unit 8 a is arranged outside the car navigation unit 8 a.This two-way transmission antenna 9 a for short-range radiocommunication is covered with a resin case or the like that does notrestrict the radiation pattern characteristic of the antenna 9 a.

As a result of employing such arrangement, it is obvious that thecommunication area is not restricted by the sheet metal chassis 8 b andthe short-range radio communication environment is further improved.Furthermore even in the case that the car navigation unit 8 a isarranged at a place where the radio environment is not desirable, it ispossible to achieve a favorable short-range radio communication with thecellular phone 2 b. Particularly in the case that the car navigationunit 8 a is arranged in the trunk, or even in the case that the unit 8 ais covered with a protective sheet metal for protection from “externalpressure” “water drop”, arranging the two-way transmission antenna forshort-range radio communication outside the car navigation unit 8 amakes it possible to stably secure the communication-available areairrespective of the place where the car navigation unit 8 a main body isarranged.

Embodiment 3.

FIG. 3 is a schematic view showing an arrangement according toEmbodiment 3 of the invention. FIG. 3 shows Example 1 of the aspect ofarranging the two-way transmission antenna 9 a for short-range radiocommunication of the car navigation unit 8 a outside the car navigationunit 8 a. In this Example 1 showing the aspect of arranging the two-waytransmission antenna 9 a for short-range radio communication, theantenna 9 a is arranged at the ceiling in the car room (Place A). As aresult, the radio environment between the two-way transmission antenna 9a for short-range radio communication and the cellular phone 2 b locatedat any of points α, β, γ, and δ in the car room is good in the samemanner. Influence due to the place of the person to talk to (i.e., placeof the cellular phone) in the car room is minimum.

In the case that the car navigation unit 8 a is arranged at any of thepoints a, b, and c in the vehicle, the distance between the two-waytransmission antenna 9 a for short-range radio communication and the carnavigation unit 8 a is almost equal, and fluctuation in loss caused by acable length is restrained. Furthermore, even in the case that the carnavigation unit 8 a is arranged in the trunk and the unit is coveredwith a protective sheet metal 10 for protection from “external pressure”“water drop”, it is possible to keep radio environment good between thetwo-way transmission antenna 9 a for short-range radio communication andthe cellular phone 2 b.

Embodiment 4.

FIG. 4 is a schematic view showing an arrangement according toEmbodiment 4 of the invention. FIG. 4 shows Example 2 of the aspect ofarranging the two-way transmission antenna 9 a for short-range radiocommunication of the car navigation unit 8 a outside the car navigationunit 8 a. In this Example 2 showing the aspect of arranging the two-waytransmission antenna 9 a for short-range radio communication isarranged, the antenna 9 a is arranged in an interior light module (PlaceB) in the car room, on a surface of the module or around the module. Asa result, the following advantages are obtained in addition to thosedescribed in Embodiment 3.

First, in the case of arranging the two-way transmission antenna 9 a forshort-range radio communication in the interior light module, thetwo-way transmission antenna 9 a for short-range radio communication isout of sight, and the car room looks very neat. Furthermore, the two-waytransmission antenna 9 a for short-range radio communication is wiredtogether with wiring of the interior light module, thereby workefficiency being improved.

In the case of arranging the two-way transmission antenna 9 a forshort-range radio communication on the surface of the interior lightmodule or in the vicinity thereof, not only the two-way transmissionantenna 9 a for short-range radio communication is wired together withwiring of the interior light module, but also the two-way transmissionantenna 9 a for short-range radio communication and the interior lightmodule can be installed at the same time, thereby work efficiency beingimproved.

In the foregoing description, the antenna is arranged in the interiorlight module in the car room, on the surface of the module or around themodule. The same advantages as in the interior light module are alsoobtained by arranging the two-way transmission antenna 9 a forshort-range radio communication integrally with a rearview mirror (roommirror) in the car room or by arranging the two-way transmission antenna9 a for short-range radio communication around the rearview mirror.

In other words, in the case that the antenna 9 a is arranged integrallywith the rearview mirror (room mirror), the car room looks neat. In thecase that the antenna 9 a is arranged around the rearview mirror (roommirror), a mounting member for mounting the rearview mirror (roommirror) and a mounting member for mounting the two-way transmissionantenna. 9 a for short-range radio communication can be combined, andthe rearview mirror (room mirror) and the two-way transmission antenna 9a for short-range radio communication can be arranged at the same time,thereby work efficiency being improved.

Embodiment 5.

FIG. 5 is a schematic view showing an arrangement according toEmbodiment 5 of the invention. FIG. 5 shows Example 3 of the aspect ofarranging the two-way transmission antenna 9 a for short-range radiocommunication of the car navigation unit 8 a outside the car navigationunit 8 a. In this Example 3 showing the aspect of arranging the two-waytransmission antenna 9 a for short-range radio communication, theantenna 9 a is arranged on the front seat side in the car room (Place C:the two-way transmission antenna 9 a for short-range radio communicationis arranged under the assistant driver's seat in FIG. 5). As a result,there is a possibility that the antenna 9 a is located in the vicinityof the cellular phone brought into the vehicle by the driver who issupposed to use the mentioned hands-free telephone in most cases,thereby reliability on transmitting and receiving in radio communicationbeing improved.

Embodiment 6.

FIG. 6 is a schematic view showing an arrangement according toEmbodiment 6 of the invention. FIG. 6 shows Example 4 of the aspect ofarranging the two-way transmission antenna 9 a for short-range radiocommunication of the car navigation unit 8 a outside the car navigationunit 8 a. In this Example 4 showing the aspect of arranging the two-waytransmission antenna 9 a for short-range radio, the antenna 9 a isarranged on a surface of a dashboard in the car room, inside thedashboard or around the dashboard (Place D). The portion indicated bythe half-tone dot meshing in FIG. 7 shows the Place D in an image ofactual vehicle.

As a result, in the case that the car navigation unit 8 a is arrangedeither at a point a (center console) or at a point b (under the frontseat) in the vehicle, the distance between the two-way transmissionantenna 9 a for short-range radio communication and the car navigationunit 8 a is shorter than that in the foregoing Embodiment 3 or 4, andloss caused by the cable length is reduced. Further, mounting thetwo-way transmission antenna 9 a for short-range radio communication iseasier than that in the foregoing Embodiment 3 or 4.

Furthermore, arranging the cellular phone 2 b either at the point γ orat the point δ in the car room does not cause any significantdeterioration in radio environment between the two-way transmissionantenna 9 a for short-range radio communication and the cellular phone 2b.

Embodiment 7.

FIG. 8 is a perspective view showing an arrangement according toEmbodiment 7 of the invention. FIG. 8 shows Example 5 of the aspect ofarranging the two-way transmission antenna 9 a for short-range radiocommunication of the car navigation unit 8 a outside the car navigationunit 8 a. In this Example 5 showing the aspect of arranging the two-waytransmission antenna 9 a for short-range radio communication, theantenna 9 a is arranged on a surface of the center console or floorconsole (the portion indicated by half-tone dot meshing in FIG. 8) inthe car room, inside the console or around the console. As a result,there is a possibility that the antenna 9 a is located in the vicinityof the cellular phone brought into the vehicle by the driver who issupposed to use the mentioned hands-free telephone in most cases,thereby reliability on transmitting and receiving in radio communicationbeing improved.

Consequently, in the case that the car navigation unit 8 a is arrangedeither at a point a (center console) or at a point b (under the frontseat) in the vehicle, particularly at the point a (the center console),the distance between the two-way transmission antenna 9 a forshort-range radio communication and the car navigation unit 8 a isshorter than that in the foregoing Embodiment 3 or 4, and loss caused bythe cable length is reduced. Further, mounting the two-way transmissionantenna 9 a for short-range radio communication is easier than in theforegoing Embodiment 3 or 4.

Embodiment 8.

FIG. 9 is a perspective view showing an arrangement according toEmbodiment 8 of the invention. Numeral 2 d is a cellular phone holderarranged at the place indicated by the arrow. FIG. 9 shows Example 6 ofthe aspect of arranging the two-way transmission antenna 9 a forshort-range radio communication of the car navigation unit 8 a outsidethe car navigation unit 8 a. In this Example 6 showing the aspect ofarranging the two-way transmission antenna 9 a for short-range radiocommunication, the antenna 9 a is arranged in the vicinity of thecellular phone holder in the car room (the portion indicated byhalf-tone dot meshing in FIG. 9). As a result, the antenna 9 a islocated in the vicinity of the cellular phone brought into the vehicle,thereby reliability on transmitting and receiving in radio communicationbeing improved.

Consequently, in the case that the car navigation unit 8 a is arrangedeither at a point a (center console) or at a point b (under the frontseat) in the vehicle, particularly at the point a (the center console),the distance between the two-way transmission antenna 9 a forshort-range radio communication and the car navigation unit 8 a isshorter than that in the foregoing Embodiment 3, 4 or 6, and loss causedby the cable length is reduced. Further, mounting the two-waytransmission antenna 9 a for short-range radio communication is easierthan in the foregoing Embodiment 3 or 4.

Embodiment 9.

FIG. 10 is a schematic view showing an arrangement according toEmbodiment 9 of the invention. FIG. 10 shows Example 7 of the aspect ofarranging the two-way transmission antenna 9 a for short-range radiocommunication of the car navigation unit 8 a outside the car navigationunit 8 a. In this Example 7 of the aspect of arranging the two-waytransmission antenna 9 a for short-range radio communication, theantenna 9 a is arranged on a surface of a rear tray in the car room,inside the rear tray or around the rear tray (Place E). As a result, inthe case that the car navigation unit 8 a is arranged at a point c inthe vehicle, the distance between the two-way transmission antenna 9 afor short-range radio communication and the car navigation unit 8 a isshorter than in Embodiment 3 or 4, and the loss caused by the cablelength is reduced. Further, mounting two-way transmission antenna 9 afor short-range radio communication is easier than in the foregoingEmbodiment 3 or 4.

Furthermore, arranging the cellular phone 2 b either at the point α orat the point β does not cause any significant deterioration in radioenvironment between the two-way transmission antenna 9 a for short-rangeradio communication and the cellular phone 2 b.

Embodiment 10.

FIG. 11 is a schematic view showing an arrangement according toEmbodiment 10 of the invention. FIG. 11 shows Example 8 of the aspect ofarranging the two-way transmission antenna 9 a for short-range radiocommunication of the car navigation unit 8 a outside the car navigationunit 8 a. In this Example 8 of the aspect of arranging the two-waytransmission antenna 9 a for short-range radio communication, theantenna 9 a is arranged in the trunk of the vehicle. (i.e., Place F: thetwo-way transmission antenna 9 a for short-range radio communication isarranged on the rear side of the rear tray in FIG. 11). As a result, inthe case that the cellular phone is arranged in a bag accommodated inthe trunk, the antenna 9 a is located in the vicinity of the cellularphone, thereby reliability on transmitting and receiving in radiocommunication being improved.

Further, in the case that the car navigation unit 8 a is arranged in thetrunk as shown in FIG. 11, the distance between the car navigation unit8 a and the two-way transmission antenna 9 a for short-range radiocommunication becomes shorter. Thus, loss caused by the antenna cable isreduced, thereby efficiency in mounting work being improved. When thedriver makes hands-free telephone talk using the cellular phone, it isobvious that the hands-free telephone talk is achieved just byconnecting the microphone for the driver arranged in the vicinity of thedriver's seat and the speaker for reproducing the voice of the person onthe other end of the line to the car navigation unit 8 a arranged in thetrunk.

Embodiment 11.

FIG. 12 is a schematic view showing an arrangement according toEmbodiment 11 of the invention. FIG. 12 shows Example 9 of the aspect ofarranging the two-way transmission antenna 9 a for short-range radiocommunication of the car navigation unit 8 a outside the car navigationunit 8 a. In this Example 9 of the aspect of arranging the two-waytransmission antenna 9 a for short-range radio communication, theantenna 9 a is arranged on the outer circumference of the car navigationunit 8 a (Place G). In this Embodiment 11, the car navigation unit 8 abody is arranged under the front seat. As a result, the distance betweenthe two-way transmission antenna 9 a for short-range radio communicationand the car navigation unit 8 a becomes extremely short, loss caused bythe cable length is extremely small, and mounting work is easy.

Furthermore, even in the case that the cellular phone 2 b is arranged atany of the points α, β, γ and δ, the radio environment between thetwo-way transmission antenna 9 a for short-range radio communication andthe cellular phone 2 b is improved as compared with the panel portion ofbuilt-in antenna type described in the foregoing Embodiment 1.

Embodiment 12.

FIG. 13 is a schematic view showing an arrangement according toEmbodiment 12 of the invention. FIG. 13 shows Example 10 of the aspectof arranging the two-way transmission antennas 9 a for short-range radiocommunication of the car navigation unit 8 a outside the car navigationunit 8 a. In this Example 10 of the aspect of arranging the two-waytransmission antennas 9 a for short-range radio communication, pluraltwo-way transmission antennas 9 a for short-range radio communicationare arranged (at Places D and H). In the drawing, Place D is located onthe dashboard described in Embodiment 6, and Place H is located on therear side of the rear tray described in Embodiment 9.

As a result, in the case that the cellular phone 2 b is located at anyof the points α, β, γ, and δ in the car room, a signal of the two-waytransmission antenna 9 a for short-range radio communication of Place Dis adopted, and in the case that the cellular phone 2 b is located at apoint ε in the trunk (in a bag in this case), a signal of the two-waytransmission antenna 9 a for short-range radio communication of Place His adopted, thus the communication-available space for the cellularphone 2 b becomes large. This further increases reliability on thecommunication-available area. This Embodiment 12 is particularlyeffective when the short-range radio communication system is built in alarge-sized vehicle.

In the foregoing description, the plural two-way transmission antennas 9a for short-range radio communication are arranged, and the antennas 9 aare arranged at the front and the rear sides of the vehicle. As anotherExample 1 of arranging the plural two-way transmission antennas 9 a forshort-range radio communication, it is preferable that at least one ofthe plural two-way transmission antennas 9 a for short-range radiocommunication is arranged on the right side of the longitudinal centerline of the vehicle, and at least another one of them is arranged on theleft side of the longitudinal center line of the vehicle. As a result ofemploying such an arrangement, it is possible to reduce influence of anyobstacle that shuts out in the longitudinal direction of the vehiclesuch as backrest of seat or human body in the vehicle.

As a further Example 2 of arranging the plural two-way transmissionantennas 9 a for short-range radio communication, it is preferable thatat least one of the plural two-way transmission antennas 9 a forshort-range radio communication is arranged on the right side of theseating center line of the driver's seat, and at least another one ofthem is arranged on the left side of the seating center line of thedriver's seat. As a result of employing such an arrangement, it ispossible to greatly reduce influence of the human body of the driver whouses most frequently the system of the invention such as hands-freetelephone talk system. The mentioned two-way transmission antennas 9 afor short-range radio communication arranged in this manner does notcause any significant deterioration in short-range radio communicationenvironment at any other place than the driver's seat.

As a further Example 3 of arranging the plural two-way transmissionantennas 9 a for short-range radio communication, it is preferable thatat least one of the plural two-way transmission antennas 9 a forshort-range radio communication is arranged on the front side of theseating center line of the driver's seat, and at least another one ofthem is arranged on the rear side of the seating center line of thedriver's seat. As a result of employing such an arrangement, it ispossible to greatly reduce influence of the human body of the driver whouses most frequently the system of the invention such as hands-freetelephone talk system. The two-way transmission antennas 9 a forshort-range radio communication arranged in this manner does not causeany significant deterioration in short-range radio communicationenvironment even in any other place than the driver's seat.

As a further Example 4 of arranging the plural two-way transmissionantennas 9 a for short-range radio communication, it is preferable thatat least one of the plural two-way transmission antennas 9 a forshort-range radio communication is “arranged at the panel portion 8 c ofthe short-range on-vehicle radio communication system (the carnavigation unit 8)” described in the foregoing Embodiment 1, and atleast another one of them is arranged at a place away from theshort-range on-vehicle radio communication system. As a result ofemploying such an arrangement, only one of the two-way transmissionantennas 9 a for short-range radio communication is arranged outside theshort-range on-vehicle radio communication system, and therefore themounting work is easy. The two-way transmission antennas 9 a forshort-range radio communication arranged in this manner obviouslyimproves the short-range radio communication environment as comparedwith the two-way transmission antenna 9 a for short-range radiocommunication arranged only at the panel portion 8 c of the short-rangeon-vehicle radio communication system (the car navigation unit 8) asdescribed in the foregoing Embodiment 1.

As a further Example 5 of arranging the plural two-way transmissionantennas 9 a for short-range radio communication, it is preferable thatat least one of the plural two-way transmission antennas 9 a forshort-range radio communication is “arranged on the outer circumferenceof the short-range on-vehicle radio communication system (the carnavigation unit 8)” described in the foregoing Embodiment 11, and atleast another one of them is arranged at a place away from theshort-range on-vehicle radio communication system. As a result ofemploying such an arrangement, only one of the two-way transmissionantennas 9 a for short-range radio communication is arranged outside theshort-range on-vehicle radio communication system, and the mounting workis easy. The two-way transmission antennas 9 a for short-range radiocommunication arranged in this manner obviously improves the short-rangeradio communication environment as compared with the two-waytransmission antenna 9 a for short-range radio communication arrangedonly on the outer circumference of the short-range on-vehicle radiocommunication system (the car navigation unit 8) as described in theforegoing Embodiment 11.

Embodiment 13

FIG. 14 is a block diagram of an antenna output selective circuitshowing an essential part of Embodiment 13 of the invention. ThisEmbodiment 13 is an example in which two two-way transmission antennasfor radio communication are used, and in which connection is made to theradio communication two-way transmission antenna output of whichreception level is higher. In FIG. 14, numeral 8 a is the car navigationunit having a radio communication function, and numerals 9 a-1 and 9 a-2are the two-way transmission antennas for radio communication arrangedoutside the body of the car navigation unit 8 a. Numerals 30-1 and 30-2are duplexers for switching whether to receive reception signals fromthe two-way transmission antennas 9 a-1 and. 9 a-2 for radiocommunication or transmit transmission signals to the two-waytransmission antennas 9 a-1 and 9 a-2 for radio communication. Numerals11-1 and 11-2 are band-pass filters for passing frequency bands of thereception signals received by the two-way transmission antennas 9 a-1and 9 a-2 for radio communication. Numerals 12-1 and 12-2 are low-noiseamplifiers for amplifying the reception signals that have passed throughthe band-pass filters 11-1 and 11-2. Numeral 13 is a level comparatorfor comparing a level of the reception signal of the two-waytransmission antenna 9 a-1 for radio communication and a level of thereception signal of the two-way transmission antenna 9 a-2 for radiocommunication, and numerals 14-1 and 14-2 are antenna switches forswitching the connection to either of the two-way transmission antennas9 a-1 and 9 a-2 for radio communication. Numeral 15 is an A/D converterfor converting a received analog signal into a digital signal, andnumeral 16 is a demodulation circuit for demodulating the receptionsignal converted into the digital signal and outputting the receptionsignal R. Numeral 17 is a modulation circuit for modulating atransmission signal T, numeral 18 is a D/A converter for converting themodulated transmission signal from a digital signal into an analogsignal, numeral 19 is a band-pass filter for limiting the transmissionsignal converted into the analog signal to a signal of a predeterminedfrequency band, and numeral 20 is an amplifier for amplifying thetransmission signal.

Operation is hereinafter described. The signals received by the two-waytransmission antennas 9 a-1 and 9 a-2 for radio communication areinputted to the level comparator 13 via the duplexers 30-1 and 30-2, theband-pass filters 11-1 and 11-2, and the low-noise amplifiers 12-1 and12-2. The level comparator 13 compares level of the two inputted signals(receiving signals), and the antenna switches 14-1 and 14-2 arecontrolled based on the result of the comparison. The reception signalselected by the antenna switch 14-1 passes through the A/D converter 15and the demodulation circuit 16, and is processed by a signal processor(not shown) in a later stage.

On the other hand, a transmitting signal is inputted to the antennaswitch 14-2 via the modulation circuit 17, the D/A converter 18, theband-pass filter 19, and the amplifier 20. As described above, theantenna switch 14-2 is controlled to select the two-way transmissionantenna for radio communication of the higher receiving signal level.Therefore, the transmission signal is transmitted from the two-waytransmission antenna for radio communication of the higher receptionlevel.

Timing for switching from one of the duplexers 30-1 and 30-2 to theother is decided on the basis of a transmission-reception switch signalS to prevent a signal from missing at the moment of switching. Further,timing for switching from one of the antenna switches 14-1 and 14-2 forselecting either of the two two-way transmission antennas for radiocommunication to the other switch is also decided on the basis of thetransmission-reception switch signal S inputted to the level comparator13.

INDUSTRIAL APPLICABILITY

The present invention is applicable to installation of a short-rangeon-vehicle radio communication system having in-car radio communicationfunction in a large-sized vehicle such as bus or train, a passenger car,or a commercial car.

1. A short-range on-vehicle radio communication system having an in-carradio communication function, comprising: a car navigation unit having amain body including a sheet metal chassis portion and a panel portionattached directly to the sheet metal chassis portion; at least a firstand a second two-way transmission antenna for short range radiocommunication, each antenna being connected with the main body by anantenna cable, each antenna being able to receive and to transmit radiocommunication signals and each antenna being arranged inside the vehicleand outside the sheet metal chassis of the main body of the radiocommunication system, wherein the first two-way transmission antenna isarranged in the interior car room and the second two-way transmissionantenna is arranged in the trunk of the vehicle; at least one mobilephone, the mobile phone communicating with the car navigation unit byusing one of the first and second two-way transmission antennas, wheresignals transmitted and received from outside the vehicle aretransmitted to and received from the at least one mobile phone via thecar navigation unit; wherein an antenna output of the highest receptionlevel is selected from the at least first and second two-waytransmission antennas for radio communication; at least one microphoneconnected to said main body used to obtain signals from within theinterior of the vehicle; and at least one speaker connected to said mainbody used to reproduce signals received at said main body, within theinterior of the vehicle.
 2. The short-range on-vehicle radiocommunication system according to claim 1, wherein the short-rangeon-vehicle radio communication system is a car vehicle navigation unit,and the first two-way transmission antenna for radio communication isarranged at the panel portion outside the sheet metal chassis of thevehicle navigation unit.
 3. The short-range on-vehicle radiocommunication system according to claim 1, wherein the first two-waytransmission antenna for radio communication is arranged outside themain body.
 4. The short-range on-vehicle radio communication systemaccording to claim 3, wherein the first two-way transmission antenna forradio communication is arranged at a ceiling of the vehicle.
 5. Theshort-range on-vehicle radio communication system according to claim 4,wherein the first two-way transmission antenna for radio communicationis arranged in an interior light module on the ceiling of the vehicle,on a surface of the module or around the module.
 6. The short-rangeon-vehicle radio communication system according to claim 3, wherein thefirst two-way transmission antenna for radio communication is arrangedon a surface of a rear tray in the vehicle, inside the rear tray oraround the rear tray.
 7. The short-range on-vehicle radio communicationsystem according to claim 3, wherein the first two-way transmissionantenna for radio communication is arranged on an outer circumference ofthe main body.
 8. The short-range on-vehicle radio communication systemaccording to claim 1, wherein the first two-way transmission antenna forradio communication is arranged on a front seat side in the vehicle. 9.The short-range on-vehicle radio communication system according to claim8, wherein the first two-way transmission antenna for radiocommunication is arranged on a surface of a dashboard in the vehicle,inside the dashboard or around the dashboard.
 10. The short-rangeon-vehicle radio communication system according to claim 8, wherein thefirst two-way transmission antenna for radio communication is arrangedon a surface of either a center console or a floor console in thevehicle, inside the console or around the console.
 11. The short-rangeon-vehicle radio communication system according to claim 8, wherein thefirst two-way transmission antenna for radio communication is arrangedin the vicinity of a cellular phone holder in the vehicle.